Bile salt activated lipase (BAL) is an important enzyme constituent of human milk. The major physiologic role of this enzyme is to enhance the fat absorption in the human infant. The objective of this research proposal is to provide new knowledge regarding the physical-chemical, chemical and immunologic properties of this lipolytic enzyme and to establish its substrate specificity, bile acid activation and kinetic mechanism. We shall also investigate the immunochemical homology between the BAL and human post-heparin plasma triglyceride lipase (TGL) and develop a specific procedure for differentiating various lipolytic activities in human post-heparin plasma. This study may provide basic information on the structure of BAL and its role in the fat absorption in human infants as well as new insight into the catalytic processes governing the catabolism of human plasma triglyceride-rich lipoproteins.